The invention concerns a current-sense resistor for measuring an electrical current, especially for measuring a battery current in a motor vehicle on-board electrical system.
EP 0 605 800 A1 discloses a current-sense resistor of this type, which consists of two copper plate-shaped connecting parts and an also plate-shaped low-ohm resistance element made of a resistance alloy (e.g. Cu84Ni4Mn12), wherein the resistance element is placed between the connecting parts and welded to the connecting parts. Such current-sense resistors are used to measure the electrical current as per the well-known four-wire technology, wherein the current to be measured is conducted through the resistance element via the plate-shaped connecting parts. The voltage drop over the resistance element then forms a measure for the electrical current to be measured in accordance with Ohm's law. The known current-sense resistor consequently has two voltage contacts on both plate-shaped connecting parts with the voltage contacts arranged near the resistance element and thus allowing a measurement of the voltage drop over the resistance element. Such current-sense resistors exhibit only a relatively low temperature dependency of the measurement, since, usually, the resistance material used (e.g. Cu84Ni4Mn12) has a very low temperature coefficient. However, the demands on temperature constancy of such current-sense resistors are still increasing.
U.S. Pat. No. 5,999,085 discloses a low-ohm current-sense resistor which has an incision on each connecting part which divides the connecting parts into a voltage contact and a current contact each. Both current contacts are used for introducing the current to be measured into or conducting it away from the current-sense resistor. Both voltage contacts serve, in contrast, to measure the electric voltage that decreases over the current-sense resistor according to the well-known four-wire technology. Here, the incision in the connecting parts runs parallel to the current flow direction between both connecting parts and therefore does not have a particularly favorable effect on the temperature stability of the current measurement. Here, the incisions in particular have a very limited influence on the current course in the connecting parts since they are oriented parallel to the main current direction.
Therefore, the object of the invention is to improve the temperature constancy of the above-described conventional current-sense resistor.
This object is achieved by a current-sense resistor according to the invention.